I've taken a quick look into the DIM settings and haven't noted any way of resetting the app.  Taking this into consideration, the only option I would recommend is deleting all the installed runtimes/content folders, clicking accept, and rebooting the app.  As for the log of installed files, those are handled and stored in a different folder and would most likely disappear if you uninstall content through DIM, provided you are still connected to DS.  Otherwise, this might need to be done manually.